A principal challenge for all forms of renewable energy is that their sources—solar radiation or wind, for example are more diffuse than fossil fuels. As a result, existing renewable energy technologies require substantial land resources in order to extract reasonable quantities of energy. Conventional propeller-style wind turbines (i.e., horizontal axis wind turbines) must be spaced far apart in order to avoid aerodynamic interference caused by interactions with the wakes of adjacent turbines. Wind turbines whose airfoil blades rotate around a vertical axis (i.e., vertical-axis wind turbines) have the potential to achieve higher power densities than horizontal axis wind turbines. This possibility arises in part because the swept area of a vertical axis wind turbine rotor (i.e., the cross-sectional area that interacts with the wind) need not be equally apportioned between its breadth which determines the size of its footprint and its height.
The prior art includes two vertical axis wind turbine (VAWT) designs.
One of them is the Savonius turbine being one of the simplest turbines. Aerodynamically, it is a drag-type device, consisting of two or three scoops. Looking down on the rotor from above, a two-scoop machine would look like an “S” shape in cross section. Because of the curvature, the scoops experience less drag when moving against the wind than when moving with the wind. The differential drag causes the Savonius turbine to spin.
Another form is the Darrieus turbine. In this apparatus, the airfoils are arranged so that they are symmetrical and have zero rigging angle, that is, the angle that the airfoils are set relative to the structure on which they are mounted. This arrangement is equally effective no matter which direction the wind is blowing compared to the conventional type, which must be rotated to face into the wind.
Wind turbines are designed to exploit the wind energy that exists at a location. Aerodynamic modeling is used to determine the optimum tower height, control systems, number of blades and blade shape. Wind turbines convert wind energy to electricity for distribution. Conventional horizontal axis turbines can be divided into three components. First the rotor component, which is approximately 20% of the wind turbine cost, includes the blades for converting wind energy to low speed rotational energy. Second the generator component, which is approximately 34% of the wind turbine cost, includes the electrical generator, the control electronics, and a gearbox component for converting the low speed incoming rotation to high speed rotation suitable for generating electricity. Finally, the structural support component, which is approximately 15% of the wind turbine cost, includes the tower and rotor yaw mechanism.
The present invention is fundamentally different from current practices in wind energy harvesting. This invention has the potential to concurrently alleviate many of the practical challenges associated with large horizontal axis wind turbines. The challenges are the cost and logistics of their manufacture, transportation, and installation, environmental impacts (e.g., bird and bat strikes); acoustic and radar signatures, visual signature, and general acceptance by local communities. These issues, although not strictly scientific, limit the further expansion of current wind energy technology. Current wind turbine systems are not modular and they are not expandable.
The present invention has addressed the needs for commercially viable wind turbine systems that are suitable for regions with dense population. It addresses the need for solutions in regions having lower average wind speeds. It also addressed the needs for visually appealing, quieter, modular and highly expandable solutions.